1. Field of the Invention
The present invention relates to a key sharing system, a public key cryptosystem, a signature system, a key sharing apparatus, an encryption apparatus, a decryption apparatus, a signature apparatus, an authentication apparatus, a key sharing method, an encryption method, a decryption method, a signature method, an authentication method, and programs for controlling computers to act as the above apparatuses.
2. Description of the Related Art
Conventionally, key cryptosystems employing a public key and a secret key have been used. Now that security for data communications is more highly required, such public key cryptosystems are attracting more and more attention. Signature systems for attaching a signature to messages to be transmitted, are also becoming popular.
In addition, since encryption using a public key plus decryption using a secret key requires a large amount of calculations, an alternative method of encrypting a message with a common key, encrypting this common key with a public key, and sending the message together with both the keys, and decrypting the encrypted common key with a secret key on the receiver-side, so as to decrypt the message using the decrypted common key, is also widely used.
With today's growing awareness of security, it is more demanded that key sharing systems, public key cryptosystems, and signature systems realize a system that needs only a small amount of calculations in encryption and decryption, while keeping high security.
The present invention has been made to solve the above problem, and it is an object of the present invention to provide a key sharing system, a public key cryptosystem, a signature system, a key sharing apparatus, an encryption apparatus, a decryption apparatus, a signature apparatus, an authentication apparatus, a key sharing method, an encryption method, a decryption method, a signature method, an authentication method, and programs for controlling computers to act as the above apparatuses.